Impregnated ferrous gear



July 24, 1951 v, LENEL 2,561,579

IMPREGNATED FERROUS GEAR Filed Oct. 2. 1947 INVENTOR.

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Patented July 24, 1951 IMPREGNATED FERROUS GEAR Fritz V. Lenel, Dayton, Ohio, assignor to General Motors Corporation, Detroit,'Mich., a corporation of Delaware Application October 2, 1947, Serial No. 77 7,559

2 Claims.

The invention relates to porous metal articles and is particularly concerned with porous ferrous articles having selected portions only thereof impregnated with a cupreous alloy.

It is therefore a prime object of the invention to provide a porous ferrous article having selected portions thereof impregnated with and strengthened by a cupreous metal or alloy whereby said portions only of the article are reduced in porosity and are increased in strength.

In carrying out the above object it is a further object to provide a new article of manufacture consisting of a sintered porous ferrous article having selected portions thereof impregnated with a cupreous metal for changing the physical characteristics of said portions.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing, wherein preferred embodiments of the present invention are clearly shown.

In the drawing:

Fig. 1 is a view of a gear wherein the dotted area indicates a cupreous metal impregnation of the porous structure of the gear and Fig. 2 is a gear having a different portion thereof strengthened by a cupreous metal impregnation, said portion being indicated by the dotted area.

In the manufacture of ferrous articles from metal powders, for example, iron articles or porous articles containing some carbon in the form of graphite or combined carbon or iron alloys, such as alloys which contain copper, molybdenum, nickel, etc., as an ingredient. It has been found that the strength in certain portions thereof is not sufiicient for their intended use. For example, in the manufacture of gears including such articles as toothed gears and cams from sintered ferrous powders, it is sometimes desirable to have stronger tooth portions than are provided by the sintered ferrous material or in some other cases, to have a stronger hub portion. Any of these variations heretofore have been obstacles in the path of more or less universal use of porous ferrous gears, cams and the like since strengthening selected portions of the article was an unsolved problem.

It is a known fact that impregnation of porous iron with copper or a cupreous alloy increases tremendously the strength of the porous iron part and it is therefore highly desirable to partially impregnate porous ferrous parts with copper or cupreous alloys wherein the copper or cupreous alloys is only present in selected portions for strengthening those portions which require increased strength. This selective impregnation is made possible through the method disclosed herein and reduces the cost of the article over a similar completely impregnated article. In other words, it has been known heretofore that gears, cams and the like made from porous ferrous material could be adequately strengthened for any use by impregnation by copper or cupreous alloys. However, theamount of cupreous material required for complete impregnation has often been so great as to be impractical from an economic standpoint.

Under the teachings of the present invention it is possible to impregnate only those selected portions of the gear or part which require strenghening and thereby markedly reduce the quantity of cupreous metal used thereby bringing the structure within economic possibilities.

I have found that where improvement in strength at the tooth portions of the gear are required, that it is necessary to place a predetermined quantity of cupreous metal adjacent to and in contact with the tooth portions of a sintered porous ferrous gear and then heat the assembled gear and cupreous metal to a temperature just above the melting point of the cupreous metal whereupon the impregnant melts and is drawn into the gear uniformly whereupon the gear is removed to a cooling zone wherein the impregnated metal is permitted to freeze within the selected portions of the gear which have been impregnated. If the hub portion only of the gear is to be impregnated, the cupreous material is placed adjacent to this portion and a similar procedure is used. Thus any selected portion of the gear, or for that matter, any ferrous porous article may be impregnated by the use of this method. Care should be taken to distribute the cupreou metal as uniformly as possible to prevent pools thereof forming upon the part upon melting thereof since these pools cause nonuniform impregnation to some extent. Cupreous metal in the form of strips, sheet or powder may be used according to the facility of operation.

The quantity of cupreous material used is best decided upon by trial with respect to the particular part being impregnated. Preliminary figures may be obtained by calculating the weight of the area to be impregnated and then utilizing about 28% of this weight of impregnating metal for a 5.7 gram/cc. density. However, this figure may vary in accordance with the density of the original part to be impregnated but in any event quantijacent the selected portions to be impregnated The temperature of the furnace is run up to 2,050 F. under suitable atmospheric conditions and upon melting of the cupreous material, the part is immediately placed in a cooling zone and permitted to cool. The desired selected impregnation will be noted.

In connection with cupreous alloy used it should be pointed out that pure copper may be used as an impregnant if desired, but pure copper will cause some pitting of the iron unless precautions disclosed in the Bourne Patent No..2,401,222 are practiced. In place of copper, cupreous alloys may be used for example,

#1. A low zinc brass containing 10% zinc, balance copper;

#2. Aluminum bronze containing 5% aluminum,

balance copper;

#3. A tin bronze containing 10% tin, 90% cop- #4. A lead bronze containing 3% .zinc, 4% tin,

4% lead, balance copper;

#5. A copper nickel alloy containing nickel 30%,

balance copper.

the part. It has been found that when carburiz- U5 ing parts made from ferrous material that the carburization of the cupreous metal impregnated 4 portions is very much slower than that of the non-impregnated section. Thus it is possible to substantially eliminate carburization of these portions by practicing the present invention.

Similarly dimensional changes upon carburization are markedly controlled through the use of impregnation.

While the embodiments of the present invention as herein disclosed, constitute preferred forms, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. A new article ofmanufacture consisting of an entire porous ferrous gear made from sintered metal powder wherein the tooth portions only thereof are selectively and predeterminedly impregnated with a cupreous alloy for increasing the strength of said portions.

2. A new article of manufacture consistingof an entire porous ferrous gear made from sintered metal powders wherein the hub portion only thereof is selectively and predeterminedly impregnated with a cupreous metal for increasing the strength of said portion.

FRITZ V. LENEL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

1. A NEW ARTICLE OF MANUFACTURE CONSISTING OF AN ENTIRE POROUS FERROUS GEAR MADE FROM SINTERED METAL POWDER WHEREIN THE TOOTH PORTIONS ONLY THEREOF ARE SELECTIVELY AND PREDETERMINEDLY IMPREGNATED WITH A CUPREOUS ALLOY FOR INCREASING THE STRENGTH OF SAID PORTIONS. 